This application claims the priority of German patent document 101 37 019.9, filed Jul. 30, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an antenna arrangement for a vehicle, particularly a multi-antenna arrangement.
To secure against theft and vandalism, and to improve the aerodynamics of the vehicle, conventional rod antennas for broadcast radio reception are frequently dispensed with in favor of incorporating antennas into the vehicle""s windshield or in a window (e.g., in the form of a rear window heating panel or in the form of separate antennas in the windshield and the rear window.) For example, German patent documents DE 295 21 512 U1 and EP 0 269 723 B1 disclose various diversity antenna arrangements which comprise a plurality of diversity antennas in the area of the windshield in order to improve broadcast radio reception. German patent document DE 195 35 250 A1, on the other hand, discloses the use of metal antenna structures arranged in plastic parts, e.g., the rear cover, of the vehicle bodywork.
In addition, particularly in convertibles, reversible characteristics of the windows, particularly the rear window, mean that antennas can be used only in the windshield or in the form of a rod antenna. For visual reasons, the rod antenna needs to be avoided. The windshield antenna and the antennas arranged in plastic parts are correspondingly complex and cost-intensive for reasons of electromagnetic compatibility (EMC).
One object of the invention, therefore, is to simplify the design and actuation of an antenna arrangement for a vehicle having a plurality of antennas.
This and other objects and advantages are achieved by the antenna arrangement according to the invention, which has an antenna arranged in a screen and a further antenna formed from a metal body and incorporated in a cover unit between the screen and a region in the vehicle interior. This antenna arrangement provides a diversity antenna which is of mechanically simple form and can be incorporated in a particularly simple manner. It is also subject to particularly little wear and is particularly maintenance-free. In addition, the antenna arrangement is arranged invisibly, so that neither the visual characteristics nor the aerodynamics of the vehicle are impaired. The cover unit used in this context is preferably a parcel shelf, so that no additional physical space is required for the antenna. Instead, existing componentsxe2x80x94windshield and parcel shelfxe2x80x94are used for such a diversity antenna arrangement for the vehicle. This ensures that the antenna arrangement can easily be fitted subsequently in existing vehicles.
Particularly for a vehicle with an adjustable vehicle roof where the antenna incorporated in a rear window (and hence in the region of the adjustable vehicle roof) is arranged, in the open position, in a hood, a switching device is expediently provided for changing over between the antenna incorporated in the window and the antenna incorporated in the cover unit depending on the degree of opening of an adjustable vehicle roof. In this case, when the vehicle roof is in the closed position (top up), the antenna incorporated in the rear screen is activated for signal reception. When the vehicle roof is in the open or top down position, with the rear screen in the boot hood, the switching device is used to activate the antenna in the cover unit.
Preferably, the cover unit is designed so as to be DC-isolated from the bodywork of the vehicle. That is to say that the cover unit or parcel shelf is formed from a metal part which is isolated from the vehicle bodywork. (E.g., it may be formed from a die-cast magnesium part.) This allows the whole parcel shelf to be used as an antenna.
Advantageously, the antenna formed by the cover unit is provided for broadcast radio reception in the AM range. Expediently, the antenna arranged in the window comprises a multi-antenna arrangement, and is provided for broadcast radio reception in the AM range, as well. This means that a combination of the antenna in the cover unit and the multi-antenna arrangement in the window forms a multiple diversity antenna for the AM range.
To improve the reception response for such multipath reception, the antennas each have an associated separate antenna amplifier which is arranged close to the antenna. Preferably, the cover unit is connected by means of a braid to one input of the relevant antenna amplifier grounded to the vehicle body.
Depending on the type and function of communications services and/or media provided in the vehicle, further antennas can be provided, either alternatively or additionally, in the same window or in another window, for broadcast radio reception in the FM range and/or for receiving a GPS signal. In this case, a further multi-antenna arrangement is provided in the region of the front windshield for reception in the FM/TV range. Expediently, a further switching device is provided for changing over between the antennas receiving the FM/TV range.
Depending on the quality of the reception, the switching device can be in the form of a simple switching element or in the form of a diversity processor. In this case, the conventional switching element involves changing over one antenna to another antenna when the received signal drops below a prescribed minimum. The diversity processor is used to perform an improved selection procedure, in which a continual quality comparison between the receiving antennas is used to select the optimum antenna in each case.
To coordinate the various switching devices for the respective multi-antenna arrangementxe2x80x94FM multi-antenna arrangement and AM multi-antenna arrangementxe2x80x94and also other reception antennas, such as GPS antenna, telephone antenna, emergency-call antenna, the vehicle has a control and operating unit for controlling and/or operating the switching devices. Advantageously, the control and operating unit is connected to a control unit for the adjustable vehicle roof by means of a bus system. This ensures that vehicle-related data are taken into account when controlling and/or operating the antenna arrangement. Depending on the type and form, the control and operating unit can be part of the radio or of another system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.